This invention relates generally to extracting heat from an electronic system, and more particularly, to extracting heat from a printed circuit board (PCB) using a heat transfer system embedded in the PCB.
Embedded computer systems contain very high power electrical components, typically associated with but not limited to central processing units (CPUs), in a volumetrically constrained environment. The volumes typically do not change as the power dissipation of the components increases, presenting significant challenges in the management of component temperatures. Active and passive heat-sinks comprised of highly thermally conducting materials such as aluminum and copper have been used to cool the components. As the power dissipation of the components increases, hotspots on the PCB develop which further complicates thermal management. One way of controlling hotspots is to facilitate the movement of heat from the hotspot to a more advantageously located heat-sink. This is traditionally done using heat-pipes. Heat-pipes are liquid filled tubes for transferring heat from one end of the tube to the other end of the tube. Hotspots may also be controlled by distributing the heat across more surface area of the PCB. This is done by dedicating layers of copper in the PCB for conducting heat from the component and throughout the PCB. The copper layers are also the electrical ground plane for the electronic circuits on the PCB and the heat is conducted to this layer of copper from the electrical component by way of vias. Unfortunately, as power dissipation increases, additional layers of copper are required for conducting heat from the component, leaving less area for trace routing for electrical signals in the design.
Existing systems for removing heat from a device on a PCB and spreading it across the PCB or moving it to a heat-sink located elsewhere on the PCB have disadvantages. These systems have to dedicate portions of the available volume for heat-pipe mechanisms. They also require direct contact of the device to a heat-sink, sometimes through cut-outs in the PCB, reducing available PCB area. Further, they require using copper planes for conducting heat which consumes PCB routing areas.